Penile Injections

Penile injections are said to be more effective than oral medication particularly in cases of poor arterial inflow or excessive leaking of blood out of the penis, known as venous leakage. Erectile dysfunction not responding to oral medication can be seen in the presence of chronic medical conditions such as diabetes, after prostate cancer treatment and the result of ageing.

Different types of penile injections

Penile injections are self administered by the man and are available in two forms. The first is Caverject Impulse which is available in two strengths, 10mcg and 20mcg. These are obtained with a doctor’s prescription through a local pharmacy. Different doses can be adjusted via a dial mechanism on the Caverject Impulse syringe. Video instruction on the correct use of injecting can be found on

The second form of penile injection is available through compounding chemists who have a special licence to manufacture injection medications. These are generally known as Trimix and usually involve a combination of alprostadil (PGE1), phentolamine and papaverine. The medication comes in a multi dose vial and the appropriate dose is calculated with discussion with your doctor. These compounded injections usually require refrigeration and have a short expiry date.

Side effects of penile injections

Penile injections are a very effective treatment of erectile dysfunction, particularly in the more severe cases. The known side effects are:

  1. Post injection pain, this is a chemical pain that occurs 1-2 hours after the injection. It should be noted that the actual insertion of the needle at the time of injecting is not as painful as expected.
  2. Penile scarring can occur from regular injecting and is minimised by maximising a good injecting technique.
  3. Priapism or prolonged erection is a known risk of penile injection therapy. This can be minimised by initiating a low first dose and increasing the dose slowly until the required response is obtained. Priapism is treated by applying cold packs to the penis plus the taking of Sudafed cold remedy tablets which act as a blood constrictor. If the erection persists more than 2-4 hours then a visit to the local emergency dept to deliver an antidote or drain the prolonged erection. Occasionally surgical drainage is required.

Men who use penile injections are advised not to use the injection more than 1-3 times a week and never more than once in 24 hours. Men who use penile injections should be regularly reviewed, at least every 6-12 months to check for penile scarring and to check on their injecting technique. Penile injections should only be used after full evaluation and instruction by your doctor, urologist or sexual health physician.

The intention of this handout is for educational purpose only and not to be used as a guide for self-management. Consult with your specialist or GP.

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